[JimD]

It is definitely possible, I've done it twice (once in two different 128s). It is not difficult but you have to remove the console which means pulling out a lot of stuff. You have to cut a hole in the console which made me a bit nervous, more so on the car I didn't own. The spot for the cup holder is fairly obvious when you turn the console over, however.

I use it every day to hold my coffee on the way to work. Definitely better than the two stock cup holders, but the short one holds a mini water bottle.